how can i be certain that a file has copied exactly?

[Gary Kline]

On Sat, Dec 27, 2008 at 03:29:05AM +0200, Giorgos Keramidas wrote:
> On Fri, 26 Dec 2008 17:13:39 -0800, Gary Kline <kline at thought.org> wrote:
> > is there a way i can be sure that my little C program has copied a
> > dos/win file named, say, foo.htm\;7 to simply foo.htm?
> >
> > my program uses fopen/fgets/fputs to copy the markup files.  of the
> > several i have copied, no problem.  unless i hack cmp or diff, i have
> > to avoid the shell.
> >
> > any ideas? in other words, does anybody have a prefab cmp(oldfile,
> > newfile) fn?
> 
> You don't need a prefab `cmp' function, because the base system already
> includes tools that can help:
> 
>   (a) The `cmp' utility:
> 
>             cmp file1 file2 ; echo $?
> 
>   (b) Checksum tools like `md5', `sha1' and `sha256':
> 
>             md5 file1 file2
> 
>             sha1 file1 file2
> 
>             sha256 file1 file2
> 
>       You can then compare the file checksums.  If both the md5 and
>       sha256 checksums are identical, then the files are the same[1].
> 
>       [1] There is a possibility of ``checksum collisions'', especially
>           with md5 (see [2] for more details).  But if you use two or
>           more checksum types and none of them show differences, the
>           odds of a collision are small enough for most practical
>           purposes.
> 
>       [2] http://en.wikipedia.org/wiki/Md5#Vulnerability


		the problem is that there are several thousands of these files
		with dos names and an embedded '\;'7 in the file names.  the
		shell gets in the way.  i have tried 

		sprintf(cmdbuf, "/usr/bin/cmp %s %s", orig, new);
		system(cmdbuf);

		chokes on the embedded bytes.  

		i'm thinking of using

		find . -name "*" -print -exec {} \;

		and let me program select out the file suffix.  i unlink the
		screwy dos-ish filename.  that's why i want to be sure the
		copied/renamed files are right.


> 
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-- 
 Gary Kline  kline at thought.org  http://www.thought.org  Public Service Unix
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